Disk brakes for motor vehicles normally have a brake disk which co-rotates on the hub of a wheel to be braked, against which brake disk brake pads are pressed at both sides during a braking process. The friction pads are arranged in a brake caliper which engages over the brake disk. In motor vehicles, use is preferably made of floating-caliper brakes, in which the actuator is arranged only on one side of the brake disk but, owing to the brake caliper being mounted in floating fashion, presses both friction pads against the brake disk during a braking process. The design or actuation of the actuator may be hydraulic or electromechanical.
Technical proposals for the detection of braking forces are already known. For example, DE 10 2006 029 978 B3, which is incorporated by reference, describes a method for measuring, by means of strain gauges, the elastic expansion of the brake caliper as a measure for the application force (normal force). DE 10 2005 013 142 A1, which incorporated by reference, describes the measurement of the braking force (circumferential force) on frame calipers by means of the travel measurement of two machine parts which are movable relative to one another.
The patent application WO 2012/059313 A1, which incorporated by reference, discusses a method in which a holding arm of the brake holder of a floating-caliper brake is utilized as a beam spring, the bending of which by circumferential forces on the brake disk is measured and evaluated as a measure for the acting circumferential force. DE 10 2008 042 298 A1, which incorporated by reference, describes a brake caliper for a disk brake, wherein a device for measuring the deformation of the brake caliper by a clamping force during actuation of the disk brake is provided, which device has a holder which is connected immovably to the brake caliper, the movement of which holder relative to the brake caliper is measured.
In known solutions, a hysteresis effect can arise in the measured relative displacement or stress/strain of components, such that, after the occurrence of application forces, the arrangement does not return sufficiently exactly into its original state, such that the measurements become inaccurate. This relates in particular to systems in which a deformation of the brake caliper is measured. After the application of the brake and the subsequent release thereof, components may become stuck, or may not immediately move into their initial position, or may even be permanently deformed.